This invention relates to increasing levels of 18:1 trans fatty acids in production animals, the products of which may then be fed to mammals which in turn leads to the production of CLA from ingested 18:1 trans fatty acids; a method to screen diets using a mouse model to detect the effects on milk fat production and content; and a method and device for milking a mouse.
Conjugated linoleic acid (CLA) is a mixture of positional and geometric isomers of linoleic acidxe2x80x94acids having lengths of 18 carbons with 2 conjugated double bonds. It is understood that conjugated linoleic acid is beneficial in suppressing the growth of breast cancer cells and tumeroigenesis (Wong), (Visonnes), (Cunningham), and in partitioning whole body energy (Pariza). It is also generally accepted that the cis-9, trans-11 isomer of linoleic acid is the most effective metabolically.
It is known that CLA results from the microbial biohydrogenation of polyunsaturated fatty acids (PUFA). It is also known that dairy products have been identified as the richest source of CLA""s in the American diet. It is not known whether all the CLA appearing in milk or muscle tissue of ruminants is derived from the ruminal supply or is produced by the liver or the mammary gland from the 18:1 trans fatty acid (tFA) produced in the rumen and excreted in the milk or found in the muscle. However, it is known that the trans geometry of the bond is not formed in the mammalian system but must be of dietary originxe2x80x94either by ruminal biohydrogenation or supplemented from partially hydrogenated oils.
As suggested above, trans isomers are not produced by the mammalian (including human) body. Thus, the current emphasis is to feed CLA""s to animals or humans.
Unfortunately, a diet supplement of free fatty acids or other compounds or triglycerides containing CLA, for instance a supplement of cis-9, trans-11 CLA is not always beneficial. Supplements currently available are mixtures known to be antimicrobial and, thus, their ingestion may be deleterious to digestive microbia. Studies have also shown that the eggs of laying birds failed to hatch and that tumor loads in mice decreased when such subjects were directly fed CLA. Thus, there is an indication that CLA""s inhibit meiosis. In situ production of CLA""s would prevent some of the reported side effects of CLA. In addition the in situ reaction could be directed to produce only those CLA Isomers deemed beneficial and provide consumers with the reported benefits of CLA consumption (i.e. cis-9, trans-11 CLA or others). Furthermore, the acid conditions in the human stomach may lead to isomerization of the cis-9, trans-11 CLA isomer when ingested but if precursors are fed and desaturated in situ only desired CLA""s would be produced in the tissues.
In addition, the current attempts to provide CLA""s of animal origin are difficult to control. Biohydrogenation may not stop at the CLA step and thus provide variable levels in food. The optimal dosages for maximum benefit are not known and high levels of consumption may have adverse as well as beneficial effects. Recent efforts to feed humans partially hydrogenated vegetable oils in order to increase serum CLA""s has the disadvantage of producing isomers other than cis-9, trans-11 as well as the documented adverse effects of trans 18:1 monomers and possibly other 18:1 isomers. Feeding trans-11 18:1 enriched diets would obviate deleterious effects of other isomers.
The inventors increase levels of the trans fatty acids in production animals, the products of which are then consumed by humans. In order to derive CLA benefits it is necessary for mammals to ingest fatty acid trans isomers such as the 18:1t-11 isomer. This isomer is the major isomer in dairy fat and one of the major isomers present in partially hydrogenated vegetable oils, but process dependent. The 18:1t-11 isomer is desaturated in any mammalian body by a common enzyme, delta-9 desaturase, at the n-9 position yielding cis-9, trans-11-CLA.
xe2x80x94the CLA isomer reported to be most beneficial. Likewise, certain trans 18:1 and cis 18:1 fatty acids can be desaturated by the animal liver or mammary gland at the delta-9 position. The trans 11-18:1 is one of the isomers capable of being desaturated in this manner. Providing the appropriate substrate, (i.e. trans-11-18:1, trans vaccinic acid) would allow the mammary gland to produce cis-9, trans-11-18:2 by action of the delta-9 desaturase which is active in the gland during lactation. Likewise, in beef cattle as well as dairy cows, the liver as well as other tissues are able to produce CLA""s from trans-monoene substrates.
Thus, an object of the invention is to allow for an animal or person to produce their own CLA""s in situ; such a process is under metabolic controls and at the levels that are appropriate for the individual organism.
Another object of this invention is to alter rumen conditions to lead to variations, i.e., increases in the amounts of tFA (trans 18:1) and trans-18:2 fatty acids including CLA""s produced by the production animal.
Another object of the invention is to design diets which provide the appropriate oil substrates and rumen environment to optimize the production of tFA.
Another object of the invention is to provide a method for increasing the production of cis, trans conjugated acids in a mammal comprising, feeding to a mammal the food products of production animals fed diets high in carbohydrates or diets with protected tFA, or said food products containing increased levels of 18:1 trans-11 acid as a result of consuming diets high in carbohydrates and fat.
Another object is to provide a feed supplement or feed composition that prevents lactation failure in mammals.
Another object is to provide a small animal model wherein a specific diet produced is fed to the small animal and meat and milk products are analyzed to predict milk and meat composition of larger production animals.